2.6. X Server Connection Close Operations
When the X server's connection to a client is closed
either by an explicit call to
XCloseDisplay()
or by a process that exits, the X server performs the following
automatic operations:
-
It disowns all selections owned by the client
(see
XSetSelectionOwner()).
-
It performs an
XUngrabPointer()
and
XUngrabKeyboard()
if the client has actively grabbed the pointer
or the keyboard.
-
It performs an
XUngrabServer()
if the client has grabbed the server.
-
It releases all passive grabs made by the client.
-
It marks all resources (including colormap entries) allocated
by the client either as permanent or temporary,
depending on whether the close-down mode is
RetainPermanent
or
RetainTemporary.
However, this does not prevent other client applications from explicitly
destroying the resources (see
XSetCloseDownMode()).
When the close-down mode is
DestroyAll,
the X server destroys all of a client's resources as follows:
-
It examines each window in the client's save-set to determine if it is an inferior
(subwindow) of a window created by the client.
(The save-set is a list of other clients' windows,
which are referred to as save-set windows.)
If so, the X server reparents the save-set window to the closest ancestor so
that the save-set window is not an inferior of a window created by the client.
The reparenting leaves unchanged the absolute coordinates (with respect to
the root window) of the upper-left outer corner of the save-set
window.
-
It performs a
MapWindow
request on the save-set window if the save-set window is unmapped.
The X server does this even if the save-set window was not an inferior of
a window created by the client.
-
It destroys all windows created by the client.
-
It performs the appropriate free request on each nonwindow resource created by
the client in the server (for example,
Font,
Pixmap,
Cursor,
Colormap,
and
GContext).
-
It frees all colors and colormap entries allocated by a client application.
Additional processing occurs when the last connection to the X server closes.
An X server goes through a cycle of having no connections and having some
connections.
When the last connection to the X server closes as a result of a connection
closing with the close_mode of
DestroyAll,
the X server does the following:
-
It resets its state as if it had just been
started.
The X server begins by destroying all lingering resources from
clients that have terminated in
RetainPermanent
or
RetainTemporary
mode.
-
It deletes all but the predefined atom identifiers.
-
It deletes all properties on all root windows (see section "Properties and Atoms").
-
It resets all device maps and attributes
(for example, key click, bell volume, and acceleration)
as well as the access control list.
-
It restores the standard root tiles and cursors.
-
It restores the default font path.
-
It restores the input focus to state
PointerRoot.
However, the X server does not reset if you close a connection with a close-down
mode set to
RetainPermanent
or
RetainTemporary.
Christophe Tronche, [email protected]
